Traditional surfboard manufacture utilises a blank, typically formed of polystyrene, incorporating a centreline stringer, typically formed of balsa wood, and which provides strength and rigidity to the board. The foam blank and stringer are then encased in a fiberglass shell formed of fiberglass mating and polyester resin. Whilst the peripheral shape of the board may vary depending upon the style of wave to be ridden and the skill or preference of the rider, this traditional “fibreglass” form of construction has been a standard in the industry for more than fifty years.
Other foam materials, such as polyurethane and EPS (expandable polystyrene) may be used, in which case epoxy resin is used to harden the fiberglass shell. These alternate materials have become popular over the past 5 or so years. These alternate materials are lighter in weight and are more flexible than the traditional materials. Ultra-violet stabilised epoxy resins are also now available which permit that hardener to be used with polystyrene blanks. Stringers may also be formed of plywood.
Variations on these methods of construction provide for the use of additional stringers. For example, three stringers have often been used in the formation of so-called “longboards”, having a length of about 8 feet (2.4 meters) or more. The traditional fiberglass forms of constructions are popular with relatively small local manufacturers who can easily customise shapes to the desires of their clients. Polystyrene is well suited to shaping with hand tools and the like.
Relatively recently, other forms of manufacture have evolved that are better suited to mass, substantially automated, manufacture. These generally include use of the alternate materials mentioned above. One example is the TUFLITE™ form which includes a shaped EPS foam blank laminated with thermally formed plastics layers, such as PVC.
One problem with is that the stringer is used to provide strength to the board, whilst retaining some longitudinal flexibility. Nevertheless, the boards tend to twist under pressure whilst being ridden. Maintaining transverse rigidity to avoid twisting of the board provides a more stable platform for the rider in variable conditions. Additional transverse rigidity is generally provided by increasing the size of the fiberglass coating. This can be achieved by using additional layers of fiberglass matting, or using layers of increased mass. However this can increase the weight of the board, thereby reducing its buoyancy. Even with the TUFLITE™ process mentioned above, which uses foam said to be 30% lighter than traditional foams, multiple laminations are used to increase the strength of the board.